Parasitic diseases, including malaria, trypanosomiasis, and leishmaniasis, produce an enormous disease burden throughout the world, yet development of urgently needed new drugs has proceeded at a slow pace. Parasite glucose transporters are essential for the infectious stages of malaria, African trypanosomes, and Leishmania and are genetically or pharmacologically validated targets for development of drugs. In this application, an assay will be developed for high throughput format for inhibitors of parasite glucose transporters that could represent leads for development of novel anti-parasitic drugs. This assay utilizes a glucose transporter null mutant of Leishmania mexicana that is dependent for growth, in the appropriate medium, upon functional expression of a heterologous glucose transporter transgene. This null mutant will be complemented with a transgene encoding the Plasmodium falciparum hexose transporter, PfHT, and the transgenic parasites will be assayed for growth using the alamarBlue fluorescence assay and the SYBR Green I fluorescence assay. Inhibitors of PfHT will inhibit growth of the PfHT transgenic Leishmania parasites. The assay will be optimized for a high throughput microtiter plate based format employing established statistical criteria and will subsequently be employed in an automated screen of a modest size chemical library to establish its utility for eventual high throughput screening of larger chemical libraries. Any inhibitors identified from this medium throughput screen will be further characterized to determine whether they are specific inhibitors of PfHT but not mammalian glucose transporters and whether they kill malaria parasites in culture yet display low toxicity for mammalian cells. This project will develop a high throughput screening method that can be employed in future studies to screen large libraries for high affinity, high specificity inhibitors of glucose transporters from malaria, African trypanosomes, and Leishmania parasites. The long-term promise is to make possible the identification of lead compounds for development of novel anti-parasitic drugs of great potential utility for promoting global public health. Public Health Relevance. The parasites malaria, Leishmania, and the African trypanosomes cause an enormous disease burden on a global scale, and the identification of new drugs is urgently needed. The objective of this application is to develop a screen for compounds that inhibit the uptake of the sugar glucose by these parasites. Since glucose is an essential nutrient for these parasites, such compounds would kill the parasite and could act as novel drugs for treatment of the diseases they cause.